The IEP Technologies UV/IR Flame Detector comprises a sensor module and electronic controller housed within a copper- free aluminum, explosion-proof enclosure. The sensor module incorporates an ultraviolet sensor and an infrared sensor, both of which must respond to an event before generating an alarm signal. Periodically an optical test source within the device emits radiation through the lens of each sensor to a reflective plate. The returned signal provides a periodic check of the optical surfaces, sensors, and signal processing circuitry. Units have an optional air shield for dust environments.